I have a JVC cassette deck from about 6 years ago that is one of their top-of-the-line models -- auto reversing, dual deck, and when it records, it tests the tape by recording a test signal in order to adjust its bias. Very nice.
Its one flaw is this: It's not willing to apply much torque to the tape. If it encounters a tape that has minor mechanical problems, it will flutter badly or auto-stop when a cheaper deck would have just kept it going.
Being gentle with the tape is probably meant to be a virtue, but I'm needing to copy a large collection of older tapes in very variable condition.
Is there likely to be an adjustment inside to increase the amount of torque that it can apply?
It has always been like this, which is why I don't think it's a worn-out belt, although it's conceivable that it left the factory with a belt too large or greasy. I've never opened it up.
do you refer to take up torque? (poor take up ). or does the tape crinkle at the pinch roller in play (excessive torque)? I cant quite picture the problem.....
Low take up torque has nothing to do with transport speed, so for a start, we can eliminate that. The transport speed is governed by the contact pressure between the pinch roller, and how well the tape is made to ' stick ' to the capstan by that pressure. Obviously, the capstan has to be rotating at the correct and stable speed, but if some tapes play ok, you can pretty much eliminate that also. Sometimes, excess take up torque can cause flutter, and sometimes, with some tapes only. This comes about as a result of the takeup torque overcoming the amount of stick of the tape to the capstan.
The problem can also be caused by poor freedom of mechanical rotation of the trailing tape spool. This can be as a result of a dragging reel table or the table brake not coming fully off, or poor low quality spool mechanics inside the cassette. This time, the speed variation occurs as a result of the trailing spool ' tugging ' on the tape, so again the stick between tape and capstan is reduced, and the tape slips.
If you can run the machine with the deck removed, so that you can get to the pinch roller arm, you can try pushing some extra tension onto the arm, to increase the pinch roller / tape / capstan pressure. If this produces a result, run the deck with no tape in, and see how easy it is to stop the pinch roller with your finger. If it's very easy, then either the surface of the pinch roller hasn't got enough friction - they do get ' glazed ' after a few years service - or there is insufficient spring tension on the arm, or the arm is being restricted before it is able to apply full spring tension to the pinch roller. I have seen this occur where there is a mechanical stop tab, and it is bent slightly out of alignment.
Excess takeup torque problems can be easily identified by stopping the take up spool briefly, but make sure that there is plenty of space for the tape to spill out, otherwise it will wrap up around the capstan.
Generally, these faults are fairly easy to identify, but you really do need to be looking with the deck out, so you can get a good look at the whole transport path. Good luck.
Many higher end cassette decks use low torque drives as a means of lowering the wow and flutter specs. The manufacturers intention was that only high quality cassette should be used. i.e. ones with only the lowest friction ratings. I have and older Nakamichi and a top end Akai that are like this and are particular as hell about the quality of cassettes run in them. I usually had best results with Denon tapes or the pro stuff put out by Loranger industries. Both had high quality bearing mechanisms in the cassette hubs as well as really good graphite pads in the shells. If you eliminate the tape drive as the problem take a look at the condition of the cassettes.(Use the sharpened end of a regular pencil inserted into the drive hubs of the cassette. If any drag is felt when rotating the pencil you'll need to replace the graphite pads in the shell.)
What types of cassettes are you using, exactly? I remember an issue when tape decks were more widely used, that if you used the 'long-play' tapes (90 minute or 120 minute) tapes you could have slippage and handling problems, because the tape medium was physically thinner.
Just what I was saying... New cassettes work fine. I am trying to play some older cassettes in order to transcribe them to other media. I'll follow up the other fellow's suggestion that the pinch roller pressure may be insufficient. I'll also see what triggers the auto-stop and whether something is making it stop prematurely.
You can usually repair a dragging cassette tape by swapping out the tape spools into a newer cassette shell with good graphite pads and that'll solve the problem. Just buy some name brand low bias tapes on sale at your local wal mart and swap out the spools. You can always swap them back after you get a decent copy off the old tape. I've had luck using a light silicone oil swabbed onto the the tape spools and facing surfaces inside the cassette shell just to get them to run smoothly for a play or two. Don't overdo the oil though, if it gets on the tape it's a mess to clean off you tape heads as well as the tape.( I've got two or three bottles of pure high grade silicone oil used for the shock absorbers on RC cars that works great for this. It tends to stick to whatever surface you apply it to and really does a good job at reducing surface tension) Just wet the q-tip and rub it on the inside shells and the white plastic tape hubs and reassemble. Another problem might be the tape itself. It could have with age become oily resulting in loss of friction with the drive roller. Clean your finger tips with denatured alchohol to get off any skin oils and rub a section of the tape lightly between forefinger and thumb. If it feels the least bit slippery it's started extruding oils out of the tape and/or has aqquired a layer of dirt buildup from age. If so you'll need to clean the tape as well.(I've used denatured alchohol when I couldn't find a tape cleaning solution. Cotton medical pads soaked in alchohol will do the trick. You may want to rig up a set of spindles and a hand crank to make the job bearable.) There are also services in most cities that'll clean them for you.
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